Method and apparatus for multicast management of user interface in a network access device

ABSTRACT

The present invention discloses a method and apparatus for multicast management of user interface in a network access device, which comprises setting a user multicast information table for the user interface in the network access device, IGMP protocol processing unit obtaining the user identification information from a user IGMP message, retrieving and updating the user multicast information table based on types of multicast messages; checking the user multicast information table of the user interface when multicast resources of the user interface are not sufficient, immediately terminating the multicast GSQ process and directly performing quick-leaving when the user multicast information table of a multicast group is empty, in conjunction with use of items of multicast state. The present invention can greatly enhance speed and performance of switching for multicast channels of the network access device.

TECHNICAL FIELD

The present invention relates to a method for multicast servicemanagement in a communication network access device, particularly to amethod for multicast management of user interface for enhancingswitching performance of multicast service channel and apparatus forimplementing the method.

BACKGROUND OF THE INVENTION

With increasing development in use of communication technology,multicast service (e.g. IP TV network television, IP conferencetelevision service, IP online courses and etc.) has increasingly becomea widespread and public service, which is becoming noticeable businesspoint of growth.

FIG. 1 is a schematic diagram of a typical IP multicast architecture. Amulticast routing protocol is used between a local router and a remoterouter, and can be Distance Vector Multicast Routing Protocol (DVMRP),Protocol Independent Multicast-Dense Mode (PIM-DM) and etc. Thisprotocol form a routing forwarding table for multicast based on topologyfor interfaces entering a multicast group. A group membership protocolis used between an IGMP host and the local router. For example, atypical Internet Group Management Protocol (IGMP) host notifies thelocal router by this protocol that it desires to enter a certainmulticast group and receive messages thereof, while the local routerperiodically queries whether a member of a known group within a localarea network is in an active state (i.e. whether there are still somemembers belonging to a certain multicast group in this network section)to create and maintain membership information in a directinterconnection section of the router. Also, in order to effectivelysuppress diffusion of multicast data on a link layer, multicastprotocols such as IGMP Snooping/Proxy are introduced into a networkdevice of an access layer.

As shown in FIG. 2, a network access device DSLAM (Digital SubscriberLine Access Multiplexer) effects the fimctions of IGMP Proxy/enhancedIGMP Snooping. IGMP Proxy/enhanced IGMP Snooping receives a multicastmembership report message from a user interface, analyzes IP addressesof multicast groups in the message, create a multicast forwarding tablefor the IP address of a respective multicast group and the userinterface, and forwards the message to an upper layer device. Multicastservice streams are replicated to a plurality of network interface basedon the multicast forwarding table, and each network interface can beconnected to several user terminals (e.g. STB, PC terminals) via aCustomer Premises Equipment (CPE). Multicast service often has relativehigher requirement for response speed of devices due to its highreal-time requirement and high service quality requirement for beingdirectly oriented to terminal users. For example, the device is requiredto be ms level with respect to processing on request for terminalmulticast users leaving. There exist two versions of IGMA for use(IGMAv1, IGMPv2). For a user of IGMPv1, the terminal can enter themulticast group without Leave message. For a user of IGMPv2, it iscomprised of Leave message and allows quickly reporting termination ofmembers to the network device. For a user of IGMPv1, when channels areswitched for the user, the network access device receives request forentering other channel from the user, but it can not determine whetherthe user has left the previous multicast service channel or there areother users receiving data from the previous multicast service channelat present. Now the approaches which can be used are mainly two types:A) rule of latest-request-first: DSLAM deletes the interface from themulticast group of the multicast service table and in turn the multicastdata stream stops. The shortcomings of this approach are apparent inspite of its high leaving speed: first, the system sets alatest-transmitted message for entering the multicast group from theuser as high priority so as to affect the multicast service which theuser originally makes request to enter; second, when there are aplurality of users of the multicast on the same interface, one usernewly entering the channel will have an effect on other users using thechannel. B) General Membership Query (GMQ) process including queryingwhether there are users on the interface, still transmitting themulticast data stream to the user interface if there are other usersresponding to this querying; otherwise DSLAM deletes the user interfacefrom the multicast group of the multicast service table and in turn themulticast data stream stops. The GMQ process usually requires a periodof response time according to specification of the protocol, while it isdirected to all multicast groups, and thus it is possible to result in agreat amount of interactions of IGMP protocol packets, which increaseburden of the network and affect performance of the system. For a userof IGMPv2, when channels are switched for the user, an IGMA message,which usually has one Leave message followed by two or three Joinmessages, is transmitted to the DSLAM interface connected to the user.After DSLAM receives the Leave message, two processes as follows can beused in accordance with RFC2236: A) quick-leave approach: DSLAM deletesthe interface from the multicast group of the multicast service tableand in turn the multicast data stream stops; in this approach, despitehigh leaving speed, when there are a plurality of users of the multicaston the same interface, leaving of one user will have an effect on otherusers on use. B) process of entering Group Specification Query (GPQ)including querying whether there are still other users of the multicastgroup on the interface, still transmitting the multicast data stream tothe user interface if there are other users responding to this querying;otherwise DSLAM deletes the user interface from the multicast group ofthe multicast service table and in turn the multicast data stream stops.The GSQ process usually requires a period of 1-2 seconds according tospecification of the protocol, so that when channels are switched forthe user, the response speed of the system is relatively low, theprevious multicast data stream can not stop to release interfaceresource and the newly-added multicast data stream can not be providedto the user immediately if the interface resource is limited at thattime (e.g. due to bandwidth limit), which will have an effect on serviceexperience of the user.

An improved method for channel switching in IGMP service is provided inU.S. Patent Application No. 20040117503, entitled “IGMA Expected LeaveTriggered By MAC Address”, which determines whether the Leave message istransmitted by means of tracing and comparing MAC information of users.However, this solution has the following defects: 1) the userinformation is traced and recorded only when the user enters, and whenthere are a plurality of users, the items are too many, which occupyprecious memory space in operation; 2) the tracing and recording tableof the user is so long that it takes too long time to search for match,so delay performance will be affected when the user is switched toleave; 3) this solution can not effectively solve the problem ofquick-leaving for IGMPv1 since there is no Leaving message when the userof IGMPv1 leaves multicast; 4) when switching-back of channels isperformed on users, the previous leaving multicast data stream need tobe re-established.

Thus it can be seen that an effective means for multicast service ofuser interface management is lacked in the existing network accessdevice.

SUMMARY OF THE INVENTION

The present invention proposes a method and apparatus for multicastmanagement of user interface in a network access device, which enhanceschannel switching performance of multicast service, selects protocolprocessing flows according to particular circumstances of current userwhen channel switching is performed on the user, and enhances switchingperformance of user to the most without affecting the user normallyenjoying services.

The following technical solutions are used in the present invention:

A method for multicast connection management of user interface in anetwork access device, which is connected to several user terminals viathe user interface, the method comprising: a) setting a user multicastinformation table for the user interface in the network access device,having information items at least including multicast addresses and useridentification information; b) obtaining the user identificationinformation from a user IGMP message by the network access device,retrieving the user multicast information table and adding acorresponding item containing the multicast address and the useridentification information into the user multicast information table ifthe user is new for the multicast group which he makes request forentering when said user IGMP message is a Join message, deleting theitem of the multicast group corresponding to the user identificationinformation from the user multicast information table, entering a GSQprocess and waiting for a next IGMP message when said user IGMP messageis a Leave message; c) providing a multicast data stream of request forentering to the user transmitting the Join message by the network accessdevice.

Preferably, said step b) of the method comprises performing accesscontrol checking when the network access device receives the Joinmessage: checking the user multicast information table of the userinterface when multicast resources of the user interface are notsufficient, terminating the multicast GSQ process and directlyperforming quick-leaving when the user multicast information table of amulticast group is empty.

Preferably, said step b) of the method comprises deleting the item ofthe multicast group corresponding to the user identification informationfrom the user multicast information table when said user is an IGMPv1user and entering the multicast group is time out for the user.

Preferably, in said step a) of the method, the user identificationinformation is a MAC address or IP address of the user, or otherinformation which can identify the user.

Preferably, the user multicast information table defined in the presentinvention further includes items of multicast states to identify themulticast group as “active”, “pending” or “idle” state.

According to the above definition to the multicast state, said step b)comprises setting the multicast state of the multicast group as“pending” state after deleting the item corresponding to the useridentification information in the multicast group when said user IGMPmessage is the Leave message or entering the multicast group is time outfor the user of IGMPv1, and further, updating the multicast state of themulticast group as “idle” state if there are no other users in themulticast group when the GSQ process finishes.

According to the above definition to the multicast state, processing onthe Join message in said step b) further comprises performing accesscontrol checking: checking the user multicast information table of theuser interface when multicast resources of the user interface are notsufficient, releasing bandwidth of the multicast data stream when an“idle” multicast group exists; otherwise, releasing bandwidth of themulticast data stream by the access control checking when a “pending”multicast group exists and the corresponding user identificationinformation is empty.

The present invention further provides a network access device, which isconnected to several user terminals via a user interface, characterizedin the device comprising: a user multicast information table for savinga multicast address and user identification information of the userinterface; an IGMP protocol processing unit for obtaining the useridentification information from a user IGMP message by the networkaccess device, retrieving the user multicast information table afteraccess control checking and adding a corresponding item containing themulticast address and the user identification information into the usermulticast information table if the user is new for the multicast groupwhich he makes request for entering when said user IGMP message is aJoin message, deleting the item of the multicast group corresponding tothe user identification information from the user multicast informationtable, entering a GSQ process and waiting for a next IGMP message whensaid user IGMP message is a Leave message.

Preferably, said IGMP protocol processing unit performs access controlchecking when receiving the Join message: checking the user multicastinformation table of the user interface when multicast resources of theuser interface are not sufficient, terminating the multicast GSQ processand directly performing quick-leaving when the user multicastinformation table of a multicast group is empty.

Preferably, said IGMP protocol processing unit is further for deletingthe item of the multicast group corresponding to the user identificationinformation from the user multicast information table when said user isan IGMPv1 user and entering the multicast group is time out for theuser.

Preferably, the user identification information in said user multicastinformation table is a MAC address or IP address of the user, or otherinformation which can identify the user.

Preferably, said user multicast information table of the network accessdevice further includes items of multicast states to identify themulticast group as “active”, “pending” or “idle” state.

According to the above definition to the multicast state, said IGMPprotocol processing unit sets the multicast state of the multicast groupas “pending” state after deleting the item corresponding to the useridentification information in the multicast group when the received userIGMP message is the Leave message or entering the multicast group istime out for the user of IGMPv1.

According to the above definition to the multicast state, said IGMPprotocol processing unit further updates the multicast state of themulticast group as “idle” state if there are no other users in themulticast group when the GSQ process finishes.

According to the above definition to the multicast state, said IGMPprotocol processing unit performs access control checking: checking theuser multicast information table of the user interface when multicastresources of the user interface are not sufficient, releasing bandwidthof the multicast data stream when an “idle” multicast group exists;otherwise, releasing bandwidth of the multicast data stream by theaccess control checking when a “pending” multicast group exists and thecorresponding user identification information is empty.

According to the method and apparatus for multicast management of userinterface provided in the present invention, the network access deviceupdates the user multicast information table in real-time based on themulticast service information of the users, which on one hand reducesoccupied memory resources, and on the other hand enhances speed andperformance of channel switching, while ensuring not affecting otherusers. Under the existing network framework, it can not cost more toimplement the network device described in the present invention, onlywith requirement of adding mechanism for dynamically tracing usermulticast information in software to enhance quality of service ofmulticast service.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a typical IP multicast architecture;

FIG. 2 is implementation of multicast service in a network access deviceDSLAM;

FIG. 3 is a structure schematic diagram of implementation of multicastservice in an access device in accordance with the present invention;

FIG. 4 is a user multicast information table preferably used in a userinterface of the network access device in accordance with the presentinvention;

FIG. 5A is a schematic diagram of processing on the user IGMP message ofthe network access device in accordance with the present invention;

FIG. 5B is another schematic diagram of processing on the user IGMPmessage of the network access device in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Detailed description of the preferred embodiments of the presentinvention is provided as follows in conjunction with accompanyingfigures.

FIG. 3 is a structure schematic diagram of implementation of multicastservice in an access device in accordance with the present invention. Anetwork access device 20 is connected to several CPEs via a networkinterface of the device, with each CPE connected to several set-topboxes (STB1, STB2 . . . STBN). The network access device 20 includes anIGMP protocol processing unit 21 for analyzing IP addresses of multicastgroups in a multicast membership report message, creating a multicastforwarding table 22 for the IP address of a respective multicast groupand the user interface, and forwarding the message to an upper layernetwork device after receiving the message from the network interface.The network access device 20 will provide a multicast data stream to theuser interface based on the multicast forwarding table 22.

The IGMP protocol processing unit can be implemented by means of IGMPSNOOP or IGMP Proxy. The principle of the IGMP SNOOP protocolimplementation is forming the multicast forwarding table 22 by means ofintercepting the IGMP message transmitted from the STB to the localrouter 30; the network access device 20 only forwarding the receivedmulticast packet to members of group according to the multicastforwarding table. The IGMP Proxy implements the same functions as theIGMP SNOOP does but with different mechanism: the IGMP SNOOP obtainsassociated information only by intercepting the IGMP message, while theIGMP Proxy intercepts the IGMP request from the STB, performs processingon it and then forward it to the local router 30.

According to ideas of the present invention, the network access device20 sets a user multicast information table 23 for the user interfacewith items at least including multicast addresses and useridentification information. The user multicast information table 23should be apparently distinguished from the multicast forwarding table,and is used for achieving function of multicast service management ofthe user interface to establish the user interface and multicast servicemanagement of the user terminal on the user interface.

Compared with the conventional processing of the IGMP protocolprocessing unit, the improvements of the IGMP protocol processing unitin the present invention are obtaining the user identificationinformation from an IGMP message of the user terminal, retrieving theuser multicast information table 23 and adding a corresponding itemcontaining the multicast address and the user identification informationinto the user multicast information table if the user is new for themulticast group which he makes request for entering when said user IGMPmessage is a Join message, entering a GSQ process to detect whetherthere are other users in the multicast group, while deleting the item ofthe user identification information corresponding to the user with aLeave message in the current multicast group from the user multicastinformation table 23, and waiting for a next IGMP message when said userIGMP message is the Leave message; deleting the item of the multicastgroup corresponding to the user identification information from the usermulticast information table when said user is an IGMPv1 user without aLeave message mechanism and entering the multicast group is time out.

Generally, multicast access is limited with respect to the networkaccess device. Access control checking (including user interfacesources, system resource checking and user identity checking) is neededto determine whether to provide the requested multicast data stream tothe user prior to processing on the Join message by the IGMP protocolprocessing unit. According to ideas of the present invention, it checksthe user multicast information table of the user interface whenmulticast resources of the user interface are not sufficient,terminating the multicast GSQ process and directly performingquick-leaving when the user multicast information table of a multicastgroup is empty.

FIG. 4 is a user multicast information table preferably used in a userinterface of the network access device in accordance with the presentinvention. The items of the user multicast information include multicastaddress and user identification information, in which the useridentification information may be MAC address or IP address of the userterminal or other information identifying the user. In addition, theitems may also include ones of multicast state identifying currentoperation state of the multicast at the user interface. For example, wecan use “A” to represent that the multicast is in “active” state inwhich there are members receiving the multicast data stream at the userinterface; use “B” to represent that they multicast is in “pending”state in which the multicast group is in the state of the GSQ process;use “C” to represent that the multicast is in “idle” state in whichthere is no member receiving the multicast data stream at the userinterface. The object to set the items of multicast state is that: 1)the network access device may delete the multicast in the “idle” or“pending” state when necessary to release its internal data busbandwidth; 2) when the user bandwidth resource is insufficient at theuser interface and a new multicast is making request for entering it, itis needed to release the source at the user interface; 3) reserving“pending”, “idle” states can allow the multicast user performingswitching-back of channels to rapidly establish multicast connection,and provide selection for multicast deletion at the user interface.

FIG. 5A is a schematic diagram of processing on the user IGMP message ofthe network access device in accordance with the present invention. Atstep 20, two multicast data streams (Ch. 2, Ch. 3) have already beenestablished at a user interface, and the corresponding user multicastinformation table thereof is shown as A50 in the figure. At step 51,STB1 transmits a Join request for entering the Ch. 1 multicast group,IGMP protocol processing unit retrieves the user multicast informationtable and adds a corresponding item containing the multicast address andthe user identification information into the user multicast informationtable if it is found that the user is new for the multicast group whichhe makes request for entering. The corresponding user multicastinformation table at that time is shown as A51 in the figure. At step52, STB1 performs switching of channels, which transmits a Leave messageto make request for leaving Ch. 1. IGMP protocol processing unit deletesthe item of the multicast group corresponding to the user identificationinformation from the user multicast information table, while it enters aGSQ process to query whether there are still other users of themulticast group on the interface and waits for a next IGMP message. Thecorresponding user multicast information table at that time is shown asA52 in the figure. Next, at step 53, IGMP protocol processing unitreceives the Join message for making request for entering Ch. 4transmitted by STB1, retrieves the user multicast information table andadds a corresponding item containing the multicast address and the useridentification information into the user multicast information table ifit is found that the user is new for the multicast group which he makesrequest for entering (The corresponding user multicast information tableat that time is not shown in the figure). However, as above described,multicast access is usually limited. We can assume that each userinterface can accommodate three multicast data streams because of userinterface resource-bandwidth limit. There have already existed threemulticast data streams at the user interface at that time, and thus therequest for entering multicast data stream Ch. 4 can not be immediatelyresponded to because of limit in the user interface bandwidth. The Joinmessage of STB1 is not responded to until the above GSQ process finishesand there is no user at that time, which makes the Ch. 1 multicaststream stop to release bandwidth. However, according to the idea of thepresent invention, the IGMP protocol processing unit performs accesscontrol checking when receiving the Join message, further checks theuser multicast information table of the user interface when multicastresources of the user interface are not sufficient. It can terminate themulticast GSQ process and perform quick-leaving to release bandwidthresource and thus the multicast stream Ch. 4 can be rapidly establishedsince the user multicast information table of the multicast group Ch. 1is empty. The corresponding user multicast information table at thattime is shown as A53 in the figure.

Next, we further describe the schematic diagram of processing on theuser IGMP message of the network access device in accordance with thepresent invention provided in FIG. 5B in conjunction with the usermulticast information table provided in FIG. 4. The multicast access isalso limited, so assume that each user interface can accommodate threemulticast data streams because of user interface bandwidth limit and theuser multicast information table further includes the items of multicaststate. The differences from FIG. 5A are: at step 52, STB 1 performsswitching of channels comprising transmitting a Leave message, the IGMPprotocol processing unit sets the multicast state of the multicast groupas “pending” state after deleting the user identification informationSTB1 corresponding to Ch. 1 from the user multicast information table,and enters a GSQ process to query whether there are still other users ofthe multicast group on the interface. The corresponding user multicastinformation table is shown as B52 in the figure. At step 53, IGMPprotocol processing unit receives the Join message for making requestfor entering Ch. 4 transmitted by STB1, performs access controlchecking, further checks the user multicast information table of theuser interface when multicast resources of the user interface are notsufficient, and first selectively deletes the Ch. 3 multicast stream inthe “idle” state to release bandwidth resource if the Ch. 1 multicaststate is “pending” and the Ch. 3 multicast state is “idle”. The Ch. 4multicast stream can be rapidly established after the corresponding itemcontaining the multicast address of Ch. 4 and the user identificationinformation is added into the user multicast information table. Thecorresponding user multicast information table is shown as B53 in thefigure. As shown in step 54, the multicast state of Ch. 1 is updated as“idle” state after the GSQ process finishes and it is confirmed thatthere are no other users. The corresponding user multicast informationtable at that time is shown as B54 in the figure. Such arrangement canefficiently solve the problem of response time in switching-back ofchannels performed on the user.

With respect to processing on the user IGMP message of the networkaccess device in accordance with the present invention provided in FIG.5B, if the multicast group Ch. 3 is also in the “active” state, and onlythe multicast group Ch. 1 is in the “pending” state at step 52, thecorresponding user multicast information table is shown as B52′ in thefigure. At step 53, IGMP protocol processing unit receives the Joinmessage for making request for entering Ch. 4 transmitted by STB 1,performs access control checking, further checks the user multicastinformation table of the user interface when multicast resources of theuser interface are not sufficient, determines its corresponding item ofuser identification information if the Ch. 1 multicast state is“pending”, and immediately deletes this multicast stream to release theresource occupied by the multicast data stream if the item is empty,which means there is no user. Also, the Ch. 4 multicast which the usermakes request for enter can be rapidly established after thecorresponding item containing the multicast address of Ch. 4 and theuser identification information is added into the user multicastinformation table. The corresponding user multicast information table isshown as B53′ in the figure.

While the description of the present invention has been provided inconjunction with the detailed embodiments thereof, it is obvious forthose skilled in the art to make alternatives, modifications and changesin accordance with the above description. Therefore, such alternatives,modifications and changes shall be included in the present inventionwhen falling into the sprit and scope of the invention defined by theappended claims.

1. A method for multicast connection management of user interface in anetwork access device, which is connected to several user terminals viathe user interface, the method comprising: a) setting a user multicastinformation table for the user interface in the network access device,having information items at least including multicast addresses and useridentification information; b) obtaining the user identificationinformation from a user IGMP message by the network access device,retrieving the user multicast information table and adding acorresponding item containing the multicast address and the useridentification information into the user multicast information table ifthe user is new for the multicast group which he makes request forentering when said user IGMP message is a Join message, deleting theitem of the multicast group corresponding to the user identificationinformation from the user multicast information table, entering a GSQprocess and waiting for a next IGMP message when said user IGMP messageis a Leave message; c) providing a multicast data stream of request forentering to the user transmitting the Join message by the network accessdevice.
 2. The method of claim 1, wherein said step b) of the methodcomprises performing access control checking when the network accessdevice receives the Join message: checking the user multicastinformation table of the user interface when multicast resources of theuser interface are not sufficient, terminating the multicast GSQ processand directly performing quick-leaving when the user multicastinformation table of a multicast group is empty.
 3. The method of claim1, wherein said step b) further comprises: deleting the item of themulticast group corresponding to the user identification informationfrom the user multicast information table when said user is an IGMPv1user and entering the multicast group is time out for the user.
 4. Themethod of claim 1, wherein in said step a) of the method, the useridentification information is a MAC address or IP address of the user,or other information which can identify the user.
 5. The method of claim1, wherein in said step a) of the method, the user multicast informationtable further includes items of multicast states to identify themulticast group as “active”, “pending” or “idle” state.
 6. The method ofclaim 5, wherein said step b) comprises setting the multicast state ofthe multicast group as “pending” state after deleting the itemcorresponding to the user identification information in the multicastgroup when said user IGMP message is the Leave message or entering themulticast group is time out for the user of IGMPv1.
 7. The method ofclaim 6, further comprising updating the multicast state of themulticast group as “idle” state if there are no other users in themulticast group when the GSQ process finishes.
 8. The method of claim 5,wherein processing on the Join message in said step b) furthercomprises: performing access control checking: checking the usermulticast information table of the user interface when multicastresources of the user interface are not sufficient, releasing bandwidthof the multicast data stream when an “idle” multicast group exists. 9.The method of claim 8, wherein said access control checking furthercomprises: releasing bandwidth of the multicast data stream by theaccess control checking when a “pending” multicast group exists and thecorresponding user identification information is empty.
 10. A networkaccess device, which is connected to several user terminals via a userinterface, characterized in the device comprising: a user multicastinformation table for saving a multicast address and user identificationinformation of the user interface; an IGMP protocol processing unit forobtaining the user identification information from a user IGMP messageby the network access device, retrieving the user multicast informationtable after access control checking and adding a corresponding itemcontaining the multicast address and the user identification informationinto the user multicast information table if the user is new for themulticast group which he makes request for entering when said user IGMPmessage is a Join message, deleting the item of the multicast groupcorresponding to the user identification information from the usermulticast information table, entering a GSQ process and waiting for anext IGMP message when said user IGMP message is a Leave message. 11.The network access device of claim 10, wherein said IGMP protocolprocessing unit performs access control checking when receiving the Joinmessage: checking the user multicast information table of the userinterface when multicast resources of the user interface are notsufficient, terminating the multicast GSQ process and directlyperforming quick-leaving when the user multicast information table of amulticast group is empty.
 12. The network access device of claim 10,wherein said IGMP protocol processing unit is further for: deleting theitem of the multicast group corresponding to the user identificationinformation from the user multicast information table when said user isan IGMPv1 user and entering the multicast group is time out for theuser.
 13. The network access device of claim 10, wherein the useridentification information in said user multicast information table is aMAC address or IP address of the user, or other information which canidentify the user.
 14. The network access device of claim 10, whereinsaid user multicast information table of the network access devicefurther includes items of multicast states to identify the multicastgroup as “active”, “pending” or “idle” state; said IGMP protocolprocessing unit sets the multicast state of the multicast group as“pending” state after deleting the item corresponding to the useridentification information in the multicast group when the received userIGMP message is the Leave message or entering the multicast group istime out for the user of IGMPv1.
 15. The network access device of claim14, wherein said IGMP protocol processing unit further updates themulticast state of the multicast group as “idle” state if there are noother users in the multicast group when the GSQ process finishes. 16.The network access device of claim 15, wherein processing on the Joinmessage in said IGMP protocol processing unit further comprises:performs access control checking: checking the user multicastinformation table of the user interface when multicast resources of theuser interface are not sufficient, releasing bandwidth of the multicastdata stream when an “idle” multicast group exists; otherwise, releasingbandwidth of the multicast data stream by the access control checkingwhen a “pending” multicast group exists and the corresponding useridentification information is empty.